40 EA

COTTAGE | Water Heater

1600 – 4000 W
5,400 – 13,600 BTU

Wallas 40 EA water heater

Water Heater That is Both Functional and Beautiful

Wallas 40 EA is a water heating system for off-grid cottages that can be used solely as a hot water heater for domestic water or it can also power up underfloor heating and radiators. Underfloor water heating system is an excellent alternative to air heating as it disperses dry heat evenly in the space and provides an added luxury of having comfortably warm floors to walk on. When heat transfer fluid is run underneath the flooring, there is no air blowing in the space, which can also be a relief to some, if allergies are a concern. 

Energy-efficient Wallas diesel cottage heater requires only about 0,2-04 amps, which is why a small solar panel is sufficient to recharge the 12 V battery. Fuel consumption is also so low, that a 33 liter (6 gal.) fuel tank will keep the heater running for almost six days. Wallas particularly recommends the Neste MY Renewable Diesel™, which is high-performing low carbon biofuel.  

The modern design of Wallas 40 EA is both functional and beautiful, and comes in two color options: graphite gray and winter white, which match any decor. The unit and fuel tank can also be installed in a utility room away from the eyes. 40 EA cottage heater is widely used in the Nordic Countries and it has been found to be an excellent heating option for cool summer evenings as well as freezing cold winter nights. You can transform your off-grid cottage into a perfect resting spot, where you can relax with family and friends year-round. 

Advanced Control Panel

If 40 EA is used solely as a domestic water tank heater, the only function needed is ON or OFF.

If a second water pump is installed for floor heating, the control panel allows you to set a target room temperature and the thermostat maintains a smooth ambient temperature in the space.

The simple display shows all the pertinent information at one glance.

Wallas Remote App for Remote Access

Turn your heater on remotely with the Wallas Remote App and enjoy warm water and a warm cottage upon arrival.

Monitor indoor temperature and battery voltage remotely from home to be better prepared for the day.

Adjust temperature locally with your phone without having to reach to the control panel.

Keep your heater always updated with the latest features.



Cleaner Burning

Updated software optimizes fuel consumption

Calibrated to burn renewable fossil free diesel (e.g. HVO)

Larger burner burns fuel slower resulting in ultra low NOX emissions

Extensively tested with Neste

Improved burner efficiency for more power

The Greenboost burner burns renewable fossil-free diesel cleanly and energy-efficiently.

Combustion air is pulled in from the outside and exhaust gas is safely vented  outside keeping the indoor air clean and odorless.

Fully enclosed laminar burning process warms up and dries the indoor air with no exposed flame.

Unit can be used to power up a water boiler, underfloor heating, or radiators.

Brushless blower motors have a very long life-cycle, supporting reliably long service intervals.

Durable Finnish design and manufacturing keep your heater intact for years.

Low temperature on unit and for everyone’ safety.

12 V battery is easy to recharge with a small solar panel.

Alternatively, the unit can be used in 110V/230V network with a 12 V converter.

Advanced Control Panel enables intelligent temperature control.

Wallas app heater control works locally at the cottage with no Wifi by using short-distance wireless connection.

Heater can be accessed from any location through a WiFi modem with the Wallas App.

Remote accessibility enables system updates and diagnostics.


Wallas 40 EA power


Wallas 40 EA fuel



Fuel: Diesel, HVO renewable diesel
Power: 1600-4000 W (5,400-13,600 BTU)
Operating Voltage: 12 V 
Fuel Consumption: 0,16-0,40 l/h (5.4-13.5 oz/h)
Electricity Consumption: 0,2-0,4A
EU Energy efficiency index: A+
Length: 478 mm (18 13/16″)
Width: 305 mm (12 1/64″)
Height: 740 mm (29 9/64″)
Weight: 25 kg (55 lbs.)
Colors: Graphite gray, winter white

Choose from two beautiful colors: graphite gray or winter white


Area: 60-90 m² (645-970 ft²)

Floating houses, tiny houses, container houses, cottages, houseboats


Heater without the front panel (to be chosen separately)
Advanced Control Panel, wire 5 m (16 ft)
Power cable with connector and integrated fuse 4 m (13 ft)
Fuel line 4 m (13 ft)
Separate tank feed
Accessory bag including essential clamps and screws


Stainless Steel, High-Grade Aluminum, Other Corrosion-Resistant Materials

Technical values are measured in a reference measurement wall, which is constructed to represent a typical cottage installation.  The figures allow for 10 % reserve – yours may vary.

Wallas heaters and stoves are designed to run with standard road and boat diesel, as well as renewable fossil free diesel. Check with your distributor for further details on best options for your needs.

Wallas 40 EA dimensions

Accessories in black are included in the standard package. Accessories in blue are additional. 

Wallas cottage water heater installation


For wall installation, the following is needed:

  • 4004 Exhaust through-wall head
  • 4030 30 liter tank
  • 4880 Exhaust lead-through kit
  • 4430 Remote Access system (if you’d like to control the heater remotely)
Wallas 40 EA water heater


For chimney installation, the following is needed:

  • 4880 Exhaust through-wall kit
  • 4030 30 liter tank
  • 4430 Remote Access system (if you’d like to control the heater remotely)
Wallas 40 EA cottage water heater
Wallas 40 EA water heater installation


Water pump pushes the heat transfer fluid from the lowest pipe connection into the unit, hot water boiler and the heating pipes underneath the flooring.

Heat transfer fluid must be either

  • Glycol + water mixture or
  • Dowcal 200 (propylene glycol-based heat transfer fluid) + water mixture

Pumps are thermostatically controlled to maintain a target temperature. When the target room temperature is set higher than the current room temperature, the pump is running continuously until the target temperature is reached. To maintain the temperature, the pump runs with intervals of 10 seconds ON and 5-90 seconds OFF.


The pump will maintain the water heater at 70 ° C / 158 F°. If the water temperature rises above 82 ° C / 180 F°, the burner switches off automatically for safety reasons. The burner re-starts, when the water temperature drops to 55 ° C / 130 F°. The unit attempts to maintain a target temperature of 70 ° C / 158 F°.

It is very important to not let the unit reach excessive pressure. An open expansion tank must be used at all times. Also, a 1.5 Bar over-pressure valve should be installed in the system.

To avoid all damage from flooding, there must be proper drainage in the space where unit and water boiler are installed. The expansion tank overflow pipe should also lead to the floor drain.


Wallas heaters have a fully enclosed burning process. A fan draws combustion air in and blows the exhaust gas into the outlet through a heat recovery unit. The enclosed process ensures exhaust gas will never contaminate the indoor air.

The fuel is drawn to the burner by a pump, which allows the placement of the fuel tank for instance under the cottage, where it can be easily re-filled. 

The fuel in the burner is ignited by a glow plug. The fuel vaporizes and burns with a clean, blue flame. Once ignited, the burner is constructed to maintain the heat and the glow plug turns itself off.

All the above takes place fully automatically.

Wallas cottage heaters operation

Browse product manuals, spec sheets and more in the Documents Center

Is an Air Heater More What You Are Looking for?

If a water heating system is not exactly what you are looking for, take a look at Wallas air heaters for cottages:

Note that 40 EA installation requires knowledge on plumbing. We recommend you discuss your options in detail with a Wallas professional prior to making your purchase.